Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 200407
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
907 PM MST Thu Jan 19 2017

.DISCUSSION...A few shower remain across the region this evening
which should dissipate by midnight. Dense Fog has formed in the
Lower Treasure Valley, Upper Weiser Basin and Baker Valley this
evening and will persist through the late Friday morning. This
could help ice form on road surfaces tonight. A Dense fog
advisory will be issues shortly for the Lower Treasure Valley and
Upper Weiser Basin. High and mid clouds remain across much of the
area which have kept temperatures near freezing this evening. In
addition, satellite showing more clouds moving into se Oregon this
evening ahead of a weak upper level trough will likely keep
temperatures warmer than previously forecast. Have updated
temperatures accordingly. Next system still on track for light
snow across southeast Oregon late Friday morning and into
southwest Idaho Friday afternoon. 2 to 5 inches of snow still
looks good for the northern portions of Harney and Malheur
counties. Models soundings suggest precipitation will likely be
rain in the valley east of Caldwell. Updated forecast will be out
shortly.

&&

.AVIATION...Ongoing LIFR fog near KONO and KEUL will persist through
sunrise, while fog development is likely at KMYL after 05Z.  The
next upper level system will spread snow showers across eastern
Oregon as early as 12Z Friday morning, expanding eastward into Idaho
during the day on Friday. Snow levels will hover around 3500 FT by
Friday afternoon, with KBOI likely to receive -SHRA or -SHRASN.
Expect southwest-to-southeast surface winds of 5 to 15 KT through
sunrise. Winds aloft will be southeasterly and average 30 KT through
10K FT.

Isolated showers will persist Friday night and Saturday, with the
next significant storm system moving into Oregon/Idaho early Sunday
morning. Expect widespread MVFR and local IFR in -SHSN Sunday and
Monday.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday...Southwest flow aloft
continues throughout almost all of the short term, but heights
fall and cooling aloft will occur. A series of relatively weak
embedded short wave troughs will move through this flow, bringing
scattered snow showers tonight, more widespread snow Friday into
Friday night, and more scattered snow showers Saturday. Snow
amounts are sufficient to warrant a Winter Weather Advisory for
Harney and Malheur counties, along with the Lower Treasure Valley
on the Oregon side, for Friday into Friday night. This storm will
not be nearly as strong as the one we just had, but will bring 2
to 5 inch amounts to mainly the northern halves of the two named
counties, along with 1 to 3 inch amounts in the Lower Treasure
Valley on the Oregon side. Temperatures will be a few degrees
below normal during the day, and near normal at night.

LONG TERM...Saturday night through Thursday...Active weather
pattern will continue through Tuesday, then upper level ridging
develops with an inversion developing by Thursday into the
weekend. A series of weather systems will move through the region,
with a wave arriving on Sunday, bringing a round of snow to all
locations. As the parent upper level trough digs south along the
coast, a weak shortwave breaks off the parent trough and moves
across southeast Oregon and southwest Idaho. This system on Sunday
through Monday could bring 2-4" of snow in the valleys and 4-8" of
snow in the mountains, although confidence still remains low at
this time. After the system moves through, cold northerly flow
develops and inversion conditions develop in the valleys, with
temperatures well below normal.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Dense Fog Advisory until 11 AM MST Friday IDZ012-033.
OR...Dense Fog Advisory until 11 AM MST Friday ORZ064.
     Winter Weather Advisory from 5 AM MST /4 AM PST/ to 11 PM MST
     /10 PM PST/ Friday ORZ061-063.
     Winter Weather Advisory from 11 AM to 11 PM MST Friday ORZ064.

&&

$$

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DISCUSSION...JDS
AVIATION.....MT
PREV SHORT TERM...SP
PREV LONG TERM....KA/WH



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